What details should show in sculpting
You can add detail until you get to a point where its so small your computer struggles, or you'd rather just let a texture handle it. Maybe large wrinkles or veins I'd sculpt, and the rest I do with a brush template or while texturing. Certainly around the eye I'd sculpt wrinkles and detail, as no way that can be simply covered by a brush or texture. Basically get the form as much as you can with bone structure, then past that its simply up to how much you need/want to do.